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I don't just want to wrap a passport, credit card, ID, etc. in an RF impervious wrapper. I want to block any and all tags I may have on me (known or unknown) from being read.

For that you need a "jammer tag." As I understand it, RFID works as a command/response system between the reader and the tag(s).

It starts with the reader pulsing saying "any tag"... Say there is only one tag in range. It replies with it's ID number. The reader can then try to cross-reference that number (128 bits or more?) with inventory, registered passports, Visa, etc. The tag's ID is simply an index into a database.

Suppose there are two tags in range though. Both will reply, and the reader will detect this "collision" as an attempted reply, but with multiple tags stepping on each other's replies. So the reader pulses again and says "Only tags with an ID that starts with 0..." If they still collide it'll try "Only tags that start with 00..." In other words, it will keep walking down the ID number in binary until it can differentiate the tags. Note, it will also try the "Only tags that start with 1..." too. Suppose there were 3 tags in range, with IDs "00..." and "00..." and "10..." The first collision would send it down the "00..." branch looking for unique IDs, but it can't ignore the 1s either. It is a simple binary tree traversal with the reader looking to prune branches as soon as that branch has no response or no a collision response.

As I understand it, jammer tags work by violating the protocol, and always replying with either 0s or 1s or just a random set of bits. But they always reply. So the reader can never get a clear, unambiguous read on any other tags in range. I like that idea. Why should someone be able to scan me and obtain information I have not given them permission to obtain? Jammer tags for everyone!